The client probably wants to take up the lack of a quality SSO solution out of the box with their BMC sales rep.

Building a solution is certainly an option, but to do a good (as opposed to unreliable and poor) job will cost more in BMC consulting than buying SSO Plugin. We've deliberately priced it at fewer than 20 days BMC professional services, which is about 1/3 of the time BMC typically quote to undertake (and not promise to deliver) an SSO solution.